Passive Pressure Sensor Research Articles

A large-pressure-range, large-sensing-distance wireless passive pressure sensor based on polymer infiltration pyrolysis-enhanced polymer-derived ceramic films

Large-pressure-range, large-sensing-distance evanescent-mode resonator wireless passive pressure sensors were fabricated from silicon carbonitride polymer-derived ceramic (PDC-SiCN) films enhanced by the polymer-infiltration-pyrolysis (PIP) process. The properties of PIP enhanced PDC films ensure a large pressure range for the sensor. To increase the sensing distance between the interrogation antenna and the sensor, the size or position of the resonator and slot antenna were optimized by High Frequency Structure Simulator simulations. The experimental results show that the resonant microwave signal can be wirelessly detected at distances up to 30 mm. The pressure sensor has a large pressure range (0–850 kPa) and high pressure sensitivity (211.8 kHz kPa−1) in pressure environments at room temperature.

A Capacitive Pressure Sensor Based on Cofirable Ceramic/Glass Materials with LTCC Technology

Abstract Because of good thermal, electrical, and mechanical properties, low-temperature cofired ceramic (LTCC) has shown great potential in microelectronic applications. One of the most promising directions of LTCC technology development are integrating and packing sensors. In this article, a wireless passive capacitive pressure sensor operating in the MHz range based on cofiring of heterogeneous materials with LTCC technology is proposed, and the design, simulation, and fabrication of the sensor are demonstrated and discussed. It consists of a circular spiral inductor and a capacitor of two electrodes separated by a glass medium. Furthermore, a unique process of cofiring of heterogeneous materials was introduced to avoid deformation of the capacitive embedded cavity during lamination or sintering. The results show that the inductance of the inductor and the capacitance of the capacitor embedded in the sensor are .28 μH and 16.80 pF, respectively. The novel sensor has a sensitivity of approximately 847 Hz/MPa within the pressure range from atmospheric pressure to 100 MPa.

Fabrication of a flexible wireless pressure sensor for intravascular blood pressure monitoring

This work presents the development of a wireless passive pressure sensor for cardiovascular pressure monitoring. The device is designed to be inserted into a stent that can be deployed within a blood vessel using a catheter-based delivery system. By utilizing micromachining techniques, a variable capacitor and an inductor were implemented in the sensor as an L-C resonator for wireless pressure sensing and signal retrieving. The sensor employs biocompatible polymeric material, parylene-C, as the substrate material. The pressure responses of the sensor, such as the sensitivity, linearity, and hysteresis, were measured and discussed. The sensitivity was approximately 6.19 × 10−2/kPa (8.25 × 10−3/mmHg), and the linearity over the ranges of 0–6 kPa (0–50 mmHg) and 6–33 kPa (50–250 mmHg) were approximately 91.5% and 87.6%, respectively. The wireless pressure sensing performance of the sensor was evaluated using the phase-dip technique. Additionally, the measured results indicate that the resonant frequency of the resonator shifted from 211 MHz to 182 MHz, as the pressure varied from 0 to 33 kPa (250 mmHg). The maximum standard error of the mean is 0.86 MHz. Finally, the influence of coil thickness on the wireless readout performance was investigated.

In-Situ Wireless Pressure Measurement Using Zero-Power Packaged Microwave Sensors

This paper reports the indoor wireless measurement of pressure from zero-power (or passive) microwave (24 GHz) sensors. The sensors are packaged and allow the remote measurement of overpressure up to 2.1 bars. Their design, fabrication process and packaging are detailed. From the measurement of sensor scattering parameters, the outstanding sensitivity of 995 MHz/bar between 0.8 and 2.1 bars was achieved with the full-scale measurement range of 1.33 GHz. Moreover, the 3D radar imagery technique was applied for the remote interrogation of these sensors in electromagnetic reverberant environments. The full-scale dynamic range of 4.9 dB and the sensitivity of 4.9 dB/bar between 0.7 and 1.7 bars were achieved with radar detection in a highly reflective environment. These measurement results demonstrate for the first time the ability of the radar imagery technique to interrogate fully passive pressure sensors in electromagnetic reverberant environments.

Increasing sensing distance of passive wireless IOP sensor

Continuous intraocular pressure monitoring is very necessary for glaucoma patients. In this paper, a passive wireless intraocular pressure (IOP) sensor using an inductively coupled wireless sensing technique is presented. IOP sensor is consist of a multipath circular spiral coil inductor, variable capacitor and a SU-8 pressure sensitive diaphragm. Capacitor and inductor of sensor are made of high-conductivity and biocompatible metal gold that are encapsulated inside biocompatible SU-8 to prevent damage to eye tissue. By measuring impedance phase dip frequency shift from the external reader coil, the intraocular pressure signal is obtained from the IOP sensor. Small size of the sensor coil due to the biological constrains reduces the sensing distance. The purpose of this paper is increasing the quality factor of sensor coil using the multipath technique in order to enhancement of sensing distance. Simulation has been taken using COMSOL Multiphysics and ADS software. The proposed structure, due to its small size could increase the sensing distance. The dimension of proposed wireless sensor and sensing distance is $$ 2.5\;{\text{mm }} \times 2.5\;{\text{mm}} $$ and 2 cm, respectively, that has a larger sensing distance and smaller size compared with previous works and its sensitivity is 4281 ppm/mmHg.

Integrated passive wireless pressure and temperature dual-parameter sensor based on LTCC technology

This paper presents a kind of passive wireless pressure and temperature integrated inductor-capacitor (LC) resonant sensor based on low temperature co-fired ceramic (LTCC) technology. The pressure sensing part is dependent on a traditional cavity capacitor. The temperature sensing part is composed of an interdigital capacitor and a planar spiral inductor. The capacitance and the resistance of inductor coil would change as a response to temperature. The LTCC material with a low Young's modulus of ~65 GPa prepared by our laboratory was used to obtain high pressure sensitivity. The experimental results showed that the prepared sensor has a pressure sensitivity of 1.16 kHz/kPa, and a temperature sensitivity of 0.062% dB/°C within the range of 140–850 kPa, 50–500 °C, respectively.

A Ceramic Diffusion Bonding Method for Passive LC High-Temperature Pressure Sensor.

Alumina ceramic is a highly promising material for fabricating high-temperature pressure sensors. In this paper, a direct bonding method for fabricating a sensitive cavity with alumina ceramic is presented. Alumina ceramic substrates were bonded together to form a sensitive cavity for high-temperature pressure environments. The device can sense pressure parameters at high temperatures. To verify the sensitivity performance of the fabrication method in high-temperature environments, an inductor and capacitor were integrated on the ceramic substrate with the fabricated sensitive cavity to form a wireless passive LC pressure sensor with thick-film integrated technology. Finally, the fabricated sensor was tested using a system test platform. The experimental results show that the sensor can realize pressure measurements above 900 °C, confirming that the fabricated sensitive cavity has excellent sealing properties. Therefore, the direct bonding method can potentially be used for developing all-ceramic high-temperature pressure sensors for application in harsh environments.

Wireless passive pressure sensor based on sapphire direct bonding for harsh environments

This study presents a wireless passive high-temperature pressure sensor based on sapphire direct bonding technology. The design, fabrication, and measurement of the sensor are demonstrated and discussed. Single-crystal sapphire is used to fabricate the sensor owing to its outstanding characteristics, and the prototype sensor consists of an inductance, a variable capacitance, and an embedded vacuum-sealed cavity formed by sapphire direct bonding. Compared with other manufacturing technologies, the sapphire direct bonding process is simple and can effectively avoid the deformation and collapse of the embedded cavity, thereby leading to a better sensor performance. A more compact sensor with greater sensitivity has been fabricated in this study. The copper interrogating antenna is employed to detect the variation in the sensor’s resonant frequency caused by the pressure applied. The characterization in high-temperature pressure environments successfully demonstrates the sensing capabilities for pressures from 20 kPa to 600 kPa up to 600 °C. At 600 °C, the sensor sensitivity reaches as high as 10 kHz/kPa. The proposed sensor can be applied for the monitoring of gas pressure in harsh environments, such as environments with high temperatures and chemical corrosion.

Design of small size and high sensitive less‐invasive wireless blood pressure sensor using MEMS technology

This study presents an implantable passive wireless blood pressure sensor using an inductive coupling wireless sensing technique that is designed for long-term monitoring of blood pressure in hypertension patients. This sensor includes a gold tapered square spiral inductor and a circular capacitor with a polyimide diaphragm. The purpose of this study is to minimise the dimension of the sensor due to the limitation of space around the vessel; therefore, a microelectromechanical systems (MEMS) inductor and a capacitor with small dimension and high sensitivity are used. In this structure, the diaphragm is deflected by applied pressure which capacitance and then resonance frequency are changed. These changes are sensed remotely with inductive coupling, which eliminates the need of wires connection for monitoring. In this method, a blood pressure signal can be obtained by measuring the impedance phase dip from the external coil. The distance between two coils is 8 mm. The sensor is designed to provide a resonance frequency range of 282-381 MHz for a pressure range of 0-250 mmHg. Simulation has been done using COMSOL Multiphysics and ADS software. The dimension of the sensor is 2.2 mm × 2.2 mm and the sensitivity of the sensor is 1550. This sensor has a small size and high sensitivity rather than previous works.

Wireless Passive Intracranial Pressure Sensor Based on a Microfabricated Flexible Capacitor

This paper presents a wireless passive pressure sensor based on a microfabricated flexible pressure-sensitive capacitor specifically designed to monitor intracranial pressure (ICP) in patients with traumatic brain injuries. The flexible pressure-sensitive capacitor is featured by creatively utilizing the PDMS wrinkles spontaneously generated during PDMS etching to construct a cavity structure for sensitivity improvement. Moreover, a flexible reader coil used for signal readout was optimized to perform better coupling with the sensor in a large enough detection range for ICP monitoring. In addition, the flexible pressure-sensitive capacitor is capable of conforming to curved topographies of skulls and dura maters due to its flexible character and thin thickness. The experimental results show that the proposed sensor reaches a lower resonant frequency, a higher quality factor, and a better sensitivity, compared with previous reports. The abovementioned flexible character and favorable performances make the proposed sensor a potential candidate for the future application in ICP monitoring.

Erratum to “a passive wireless microelectromechanical pressure sensor for harsh environments” [feb 18 73-85

In the above paper [1] , references [46] and [54] were cited incorrectly. The corrected references are as follows.

A Passive Wireless Microelectromechanical Pressure Sensor for Harsh Environments

A microelectromechanical systems (MEMS) capacitive-type passive wireless pressure sensor designed to operate in harsh environments at temperatures up to 1000 °C is presented. The pressure sensor has a sapphire-based diaphragm and structural body, and a platinum-based capacitive element. The capacitive element is configured as a part of a slot patch antenna that is designed to operate in a far-field sensing mechanism with a Ku-band electrical resonant frequency of 15 GHz. The electrical ground plane resides on the backside of the diaphragm, which deflects in response to an applied pressure. The electrical resonant frequency of the pressure sensor changes as a function of the applied pressure to the diaphragm. An increase in the applied pressure, for example, results in a decrease in the electrical resonant frequency. The sensitivity of the pressure sensor is related to the change in applied pressure to the change in the electrical resonant frequency. Three proof-of-concept dynamic pressure sensors are reported using silicon-based diaphragms with antenna diameters of 5.6, 5.7, and 5.8 mm, and measured sensitivities of 2.2, 2.2, and 5.1 kHz/Pa, respectively, up to 900 Pa. In addition, three proof-of-concept static pressure sensors are reported with corresponding measured sensitivities of 3.4, 3.1, and 2.5 kHz/Pa up to 900 Pa. A high-temperature dynamic pressure sensor designed for harsh environments is also reported using a sapphire-based diaphragm with an antenna diameter of 3.8 mm and measured sensitivity of 21.7 kHz/Pa up to 800 Pa. [2017-0210]

Fabrications and Performance of Wireless LC Pressure Sensors through LTCC Technology.

This paper presents a kind of passive wireless pressure sensor comprised of a planar spiral inductor and a cavity parallel plate capacitor fabricated through low-temperature co-fired ceramic (LTCC) technology. The LTCC material with a low Young’s modulus of ~65 GPa prepared by our laboratory was used to obtain high sensitivity. A three-step lamination process was applied to construct a high quality cavity structure without using any sacrificial materials. The effects of the thickness of the sensing membranes on the sensitivity and detection range of the pressure sensors were investigated. The sensor with a 148 μm sensing membrane showed the highest sensitivity of 3.76 kHz/kPa, and the sensor with a 432 μm sensing membrane presented a high detection limit of 2660 kPa. The tunable sensitivity and detection limit of the wireless pressure sensors can meet the requirements of different scenes.

A wireless passive pressure sensor based on aperture coupled microstrip patch antenna

PurposeThis paper aims to present a novel wireless passive pressure sensor based on an aperture coupled microstrip patch antenna embedded with an air cavity for pressure measurement.Design/methodology/approachIn this paper, the sensitive membrane deformed when pressure was applied on the surface of the sensor and the relative permittivity of the mixed substrate changed, resulting in a change in the center frequency of the microstrip antenna. The size of the pressure sensor is determined by theoretical calculation and software simulation. Then, the sensor is fabricated separately as three layers using printed circuit board technology and glued together at last. The pressure test of the sensor is carried out in a sealed metal tank.FindingsThe extracted resonant frequency was found to monotonically shift from 2.219 to 1.974 GHz when the pressure varied from 0 to 300 kPa, leading to an average absolute sensitivity of 0.817 MHz/kPa.Research limitations/implicationsThis pressure sensor proposed here is mainly to verify the feasibility of this wireless passive maneuvering structure, and when the base material of this structure is replaced with some high-temperature-resistant material, the sensor can be used to measure the pressure inside the aircraft engine.Originality/valueThe sensor structure proposed here can be used to test the pressure in a high-temperature environment when the base material is replaced with some high-temperature-resistant material.

Passive Downhole Pressure Sensor Based on Surface Acoustic Wave Technology.

A passive surface acoustic wave (SAW) pressure sensor was developed for real-time pressure monitoring in downhole application. The passive pressure sensor consists of a SAW resonator, which is attached to a circular metal diaphragm used as a pressure transducer. While the membrane deflects as a function of pressure applied, the frequency response changes due to the variation of the SAW propagation parameters. The sensitivity and linearity of the SAW pressure sensor were measured to be 8.3 kHz/bar and 0.999, respectively. The experimental results were validated with a hybrid analytical–numerical analysis. The good results combined with the robust design and packaging for harsh environment demonstrated it to be a promising sensor for industrial applications.

A Wireless Passive Pressure and Temperature Sensor via a Dual LC Resonant Circuit in Harsh Environments

This paper presents a passive wireless sensor for simultaneously and remotely measuring pressure and temperature under harsh environments. The sensor consists of a dual $LC$ (inductor and capacitor) resonant circuit, one without a cavity and the other with a cavity capacitor for temperature and pressure sensing, respectively. The low-temperature co-fired ceramic technology is used to fabricate the sensor, making it suitable for high-temperature harsh environment operations. Experimental results show the prototype sensor has temperature sensitivity of 8.15 kHz/°C and pressure sensitivity of 1.96 MHz/Bar up to 400°C. [2016-0157]

A 0.6 V and 0.395 pJ/bit nonius TDC for a passive RFID pressure sensor tag

This work presents a nonius time to digital converter (TDC) adapted to a passive RF identification (RFID) pressure sensor tag. The proposed converter exploits the characteristics of time-based sensor interfaces and allows reducing voltage supply and power consumption while maintaining resolution and conversion efficiency. The nonius TDC has been designed and fabricated using the TSMC 90 nm standard CMOS technology. The main blocks of the converter are described and both the resolution adjustment and measurement processes are explained in detail. Measurement results show 10.49 bits of effective resolution for an input time range from 28.19 to 42.93 μs. With a sampling rate of 19 KS/s the converter has a conversion efficiency of 0.395 pJ/bit with a voltage supply of only 0.6 V. This characteristics in the proposed nonius TDC enables an increased reading range of the passive RFID pressure sensor tag.

Design of a 0-50 mbar pressure measurement channel compatible with the LHC tunnel radiation environment

The monitoring of cryogenic facilities often require the measurement of pressure in the sub 5’000 Pa range that are used for flow metering applications, for saturated superfluid helium, etc. The pressure measurement is based on the minute displacement of a sensing diaphragm often through contactless techniques by using capacitive or inductive methods. The LHC radiation environment forbid the use of standard commercial sensors because of the embedded electronics that are affected both by radiation induced drift and transient Single Event Effects (SEE). Passive pressure sensors from two manufacturers were investigated and a CERN designed radiation-tolerant electronics has been developed for measuring variable-reluctance sensors. During the last maintenance stop of the LHC accelerator, four absolute pressure sensors were installed in some of the low pressure bayonet heat exchangers and four differential pressure sensors on the venturi flowmeters that monitor the cooling flow of the 20.5 kA current leads of the ATLAS end-cap superconducting toroids. The pressure sensors operating range is about 1000 to 5000 Pa and the targeted uncertainty is +/- 50 Pa which would permit to measure the equivalent saturation temperature at 1.8 K within better than 0.01 K. This paper describes the radiation hard measuring head that is based on an inductive bridge, its associated radiation-tolerant electronics that is installed under the LHC superconducting magnets or the ATLAS detector cavern; and the first operational experience.

Highly Sensitive Reentrant Cavity-Microstrip Patch Antenna Integrated Wireless Passive Pressure Sensor for High Temperature Applications

A novel reentrant cavity-microstrip patch antenna integrated wireless passive pressure sensor was proposed in this paper for high temperature applications. The reentrant cavity was analyzed from aspects of distributed model and equivalent lumped circuit model, on the basis of which an optimal sensor structure integrated with a rectangular microstrip patch antenna was proposed to better transmit/receive wireless signals. In this paper, the proposed sensor was fabricated with high temperature resistant alumina ceramic and silver metalization with weld sealing, and it was measured in a hermetic metal tank with nitrogen pressure loading. It was verified that the sensor was highly sensitive, keeping stable performance up to 300 kPa with an average sensitivity of 981.8 kHz/kPa at temperature 25°C, while, for high temperature measurement, the sensor can operate properly under pressure of 60–120 kPa in the temperature range of 25–300°C with maximum pressure sensitivity of 179.2 kHz/kPa. In practical application, the proposed sensor is used in a method called table lookup with a maximum error of 5.78%.

Alumina ceramic based high-temperature performance of wireless passive pressure sensor

A wireless passive pressure sensor equivalent to inductive-capacitive (LC) resonance circuit and based on alumina ceramic is fabricated by using high temperature sintering ceramic and post-fire metallization processes. Cylindrical copper spiral reader antenna and insulation layer are designed to realize the wireless measurement for the sensor in high temperature environment. The high temperature performance of the sensor is analyzed and discussed by studying the phase-frequency and amplitude-frequency characteristics of reader antenna. The average frequency change of sensor is 0.68 kHz/°C when the temperature changes from 27°C to 700°C and the relative change of twice measurements is 2.12%, with high characteristic of repeatability. The study of temperature-drift characteristic of pressure sensor in high temperature environment lays a good basis for the temperature compensation methods and insures the pressure signal readout accurately.